Conventionally, pneumatic tires (hereafter, tires) widely use a method in which a main groove extending in a tire circumferential direction is formed in a tread in order to improve drainage of rain water entering a space between a road surface and the tread.
For example, a tire is known which is provided with protrusions protruding from a groove bottom portion of the main groove and extending in a tread width direction in order actively drain rain water entering the main groove (for example, Patent Document 1). Such a tire generates a water flow in rain water entering the main groove and thereby drainage is improved.